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Unit 8 Notes: Circular Motion
Velocity has both magnitude and direction, so if an object’s direction
changes, it _________________________ even if the speed remains constant.
When an object moves in a circular path, it is accelerating because its
direction is always changing. This is called ___________________________
__________________________________.
Centripetal means _______________________ _______________________.
The force making or allowing the object to move in a circular path is
called a ________________________ ____________________. It can come
from friction, gravity, the tension in a string, etc.
Useful equations for circular motion:
1. A 615 kg racing car completes one lap in 14.3 s around a circular
track with a radius of 50.0 m. The car moves at a constant speed.
a. Calculate its centripetal acceleration.
b. How much friction is necessary to keep the car traveling in a
circle?
c. What is the coefficient of friction between the tires and the
track?
2. A carnival ride has a 2.0 m radius and rotates once each 0.90 s.
a. Find the speed of a rider.
b. Find the centripetal acceleration of a rider.
c. Find the centripetal force exerted on a 75 kg rider.
___________________________ ________________________pulls an object
toward the center of a circle instead of letting it move in a straight path.
_________________________causes a rigid, rotating object to change its
velocity. It does NOT come from the center of a circle. You apply torque
to objects that have a circular path because of their construction. (door
on hinges, merry-go-round, wrench, pencil sharpener, etc.)
Torque is most effective if it is applied _______________________________
and ___________________________ to the object.
Torque can __________________, _____________________, or
___________________________ of rotating objects.
Equation:
3. You apply 40 N of force perpendicular to a wrench that is 0.25 m
long. Calculate the torque.
4. If the angle that the force is applied changes to 30o, how is the
torque affected?
If a rotating object is in equilibrium, the __________________________________
________________ must balance the _____________________________________
____________________.
Equation:
5. Four children are riding on a see-saw. On one side of the see-saw,
Jack (22 kg) sits 1.3 m from the pivot point and Kate (20 kg) sits 1.5
m from the pivot point. On the other side of the see-saw, Andrew
(21 kg) sits
1.2 m from the pivot point. Where should Sally (19 kg)
sit to balance the see-saw?